bipolar disorder, manic depressiondopamine receptor, subtype 1 (DR1)* [HGL]
Several polymorphisms in the DR1 dopamine receptor
at 5q35.1 were analyzed in several families which display an apparently
inherited form of manic depression. No association with any
of the polymorphic markers were observed to segregate with family
members afflicted with the disease. Jensen et al., Hum.
Hered., 42:269-275, 1992.

GABA(A) receptor, subunit alpha-5 [HGL]
An allelic polymorphism in the GABA(A) receptor
alpha-5 subunit was associated with a patients who had a predominance
of manic over depressive episodes in the course of the illness. Papadimitriou
et al., Am. J. Med. Genet., 81(1):73-80, 1998.

G-protein alpha subunit gene Galphaz (GNAZ) [HGL]
A silent polymorphism was identified in exon 2
of the human G-protein alpha subunit gene Galphaz (GNAZ). The
frequency of the polymorphism was determined in a control population
and in patients with bipolar mood disorder. The data showed
a statistical trend toward a difference in the distribution of the
two alleles in patients with bipolar disease as compared to the control
subjects. This data supports earlier studies showing of a bipolar
gene on chromosome 22q11, the locus of the GNAZ gene. Takuya
et al., Am. J. Med. Genet., 88:324-328, 1999.

serotonin receptor, subtype 2C (5-HT2C) [HGL]
A structural variant for the 5-HT2C receptor has
been identified in which a cysteine at position 23 is replaced by
a serine (ser23). This variant was analyzed for allelic association
with bipolar disorder. A small, but significant, increase in
frequency of the ser23 allele was observed in female subjects with
bipolar affective disorder as compared to female controls, suggesting
that the ser23 allele may increase susceptibility to bipolar disease
in women.

serotonin transporter (5HTT or SERT)+ [HGL]
A VNTR in intron 2 of the SERT gene was studied
for association with bipolar affective disorder, unipolar depression,
and schizophrenia. There was a significant increase in frequency
of allele 12 of the VNTR in subjects with bipolar affective disorder,
but not unipolar depression or schizophrenia. Collier et al.,
Neuroreport, 7:1675-1769, 1996. Another study failed to find
a correlation between two polymorphisms (a variable number of tandem
repeats in intron 2 and a deletion/insertion polymorphism in the
transcriptional control region) in SERT and manic depression. Gutierrez
et al., Biol. Psychiatry, 43:843-847, 1998.

serotonin receptor, subtype 2A (5-HT2A) [HGL]
Brains of depressed suicide victims had an overabundance
of serotonin receptors, subtype 2A (5-HT2A). This finding was
also observed in platelet 5-HT2A receptors of patients who had persistent
suicidal fantasies. A polymorphism in the 5-HT2A receptor (102C
and 102T alleles) was studied in these patients. There was
a significant association between the 102C allele in 5-HT2A receptor
gene and major depression. Patients who had both copies, the
102C/C genotype, had a higher score for suicide ideation than patients
with the T/C or T/T genotype. These results suggest that the
102T/C polymorphism in 5-HT2A receptor gene is primarily associated
with suicidal ideation in patients with major depression. Du
et al., Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:56-60, 2000.